n pl :  a bacterium of the genus Fusobacterium (F. nucleatum syn. F. fusiforme) and a spirochete of the genus Treponema (T. vincentii syn. Borrelia vincentii) that are part of the normal oral flora and undergo a great increase in numbers in the mucous membrane of the mouth and adjacent parts in Vincent's infection and Vincent's angina .
 
 
 
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